Apparatuses and methods for determining if protective coatings on semiconductor substrate holding devices have been compromised

ABSTRACT

In one aspect, the invention includes an apparatus having a semiconductor substrate receiving device with at least one extension configured to hold a semiconductor substrate within a liquid bath. The device is configured to have at least a portion of the extension at least periodically placed within the liquid bath. The extension includes a conductive material at least partially coated with an insulative protective material. The insulative protective material is configured to protect the portion of the conductive material which is in the bath from physically contacting the liquid of the bath. The apparatus also includes an electrode within the bath, and an electrical connection between the electrode and the conductive material of the extension. Additionally, the apparatus has a monitor configured to monitor a current flow state of a circuit that includes the electrode, conductive material of the extension, and liquid bath to determine if the circuit is in a closed state or in an open state. In another aspect, the invention includes methods for determining if a protective coating on a semiconductor substrate receiving device has been compromised.

RELATED PATENT DATA

This application is a continuation of U.S. patent application Ser. No.09/375,879, which was filed on Aug. 17, 1999, now U.S. Pat. No.6,411,110B1, naming Terry L. Gilton as the inventor and which isincorporated by reference herein.

TECHNICAL FIELD

The invention pertains to methodology and apparatuses associated withtreating semiconductor substrates in liquid baths. In particularaspects, the invention pertains to methodology and apparatusesassociated with determining if a protective coating on a semiconductorsubstrate receiving device has been compromised.

BACKGROUND OF THE INVENTION

In modern semiconductor processing, it is frequently desired to insertsemiconductive material wafers into liquid baths. Such baths cancomprise chemicals which would be corrosive to metal parts. Forinstance, a bath comprising H₂SO₄:H₂O₂:H₂O (6:1:1, by volume) at about120° C. is utilized for stripping photoresist as well as for cleaningorganic materials from over semiconductive material substrates. Asanother example, H₃PO₄ (85%:15% H₃PO₄ to H₂O, by volume) at about 160°C. is utilized for etching Si₃N₄. In yet another example, dilutehydrofluoric acid (about 49% hydrofluoric acid in water (by weight)) isutilized to etch oxide.

Due to the corrosive nature of baths, like those above, relative tosteel, apparatuses configured to retain semiconductive materialsubstrates within a bath typically utilize non-steel materials for thoseportions of the apparatus that will be dipped within the bath. Suchnon-steel materials include, for example, quartz and Teflon™. However,the non-steel materials can have structural disadvantages when comparedto steel. Accordingly, it can be desirable to utilize steel for portionsof a semiconductive substrate treatment apparatus that are dipped into acorrosive bath.

One method of utilizing steel for such portions of a semiconductivesubstrate treatment apparatus is to coat the steel with a protectivecoating, such as, for example, Teflon™ (polytetrafluoroethylene or PTFE)or poly(vinylidene fluoride) (PVDF). The coating provides a barrier oversteel portions of a semiconductor wafer treatment apparatus that aredipped within a corrosive bath. A problem occurring with such coatingsis that semiconductor wafers can comprise sharp edges, and such edgescan cut through the protective coatings to expose the steel materialthereunder. The exposed steel material can then be corroded by thechemicals in a bath. The corrosion can pollute the bath and eventuallydestroy the structural integrity of the steel material.

It would be desirable to develop methods for identifying if a protectivecoating provided over a steel material has been compromised. It would beparticularly desirable to develop methods which would identify acompromised protective coating before the structural integrity of anunderlying steel material is destroyed by exposure to corrosive baths.

SUMMARY OF THE INVENTION

In one aspect, the invention includes an apparatus configured to measurean electrical conductivity between an insulatively coated conductivesemiconductor substrate receiving device and a bath within which thedevice is submerged. Such measurement can determine if the insulativecoating has been compromised.

In another aspect, the invention includes an apparatus comprising asemiconductor substrate receiving device with at least one extensionconfigured to hold a semiconductor substrate within a liquid bath. Thedevice is configured to have at least a portion of the extension atleast periodically placed within the liquid bath. The extensioncomprises a conductive material at least partially coated with aninsulative protective material. The insulative protective material isconfigured to protect the portion of the conductive material which is inthe bath from physically contacting the liquid of the bath. Theapparatus also comprises an electrode within the bath, and an electricalconnection between the electrode and the conductive material of theextension. Additionally, the apparatus comprises a monitor configured tomonitor a current flow state of a circuit comprising the electrode,conductive material of the extension, and liquid bath to determine ifthe circuit is in a closed state (which enables a current flow) or in anopen state (which does not enable the current flow).

In yet another aspect, the invention includes methods for determining ifa protective coating on a semiconductor substrate receiving device hasbeen compromised.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic view of a semiconductor treatment apparatus ofthe present invention.

FIG. 2 is a diagrammatic view of another semiconductor treatmentapparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. patent Laws “to promote the progressof science and useful arts”(Article 1, Section 8).

An apparatus 10 encompassed by the present invention is described withreference to FIG. 1. Such apparatus is configured to determine if aprotective coating on a semiconductor substrate receiving device hasbeen compromised. The apparatus comprises a bath 12 defined by a fluid14 contained within a vessel 16. Fluid 14 can, for example, be a liquidcorrosive to metallic materials. Such liquid can comprise, for example,the phosphoric acid bath, sulfuric acid/peroxide bath, or hydrofluoricacid bath described above with reference to the prior art.

A pair of semiconductor substrate receiving devices 18 and 20 (which canalso be referred to as lifting devices) are shown partially submergedwithin the fluid 14 of bath 12. The devices 18 and 20 can be referred toas end effectors, and the protective insulative material provided overdevices 18 and 20 can be referred to as an end effector coating.

Devices 18 and 20 comprise extensions 22 and 24, respectively,configured to extend within bath 12 and configured to ultimately hold asemiconductor substrate (not shown) within fluid 14. For purposes ofinterpreting this disclosure and the claims that follow, the terms“semiconductive substrate” and “semiconductor wafer” are defined to meanany construction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above. In particular applications of the present invention, asemiconductor substrate will comprise a monocrystalline silicon wafer.

Devices 18 and 20 can be configured to be displaced relative to bath 12such that devices 18 and 20 can be lifted from, and inserted into, bath12. Semiconductor substrates can be inserted into bath 12 as devices 18and 20 are lowered into the bath, and then lifted from bath 12 asdevices 18 and 20 are removed from the bath. The cycling of devices 18and 20 into and out of bath 12 causes a portion of devices 18 and 20(notably, extensions 22 and 24) to be periodically placed within fluid14.

Devices 18 and 20 comprise a conductive material (such as, for example,steel) coated with an insulative protective material (such as, forexample, PTFE or PTVF). The insulative material protects portions of theconductive material which are inserted into the bath from physicallycontacting the liquid of the bath. Accordingly, the insulative coatingprotects conductive portions of devices 18 and 20 from being corroded bythe fluid 14 of bath 12.

In the shown embodiment, devices 18 and 20 comprise hooks at extensions22 and 24 for receiving semiconductor substrates (not shown). It is tobe understood, however, that devices 18 and 20 could comprise otherconfigurations for receiving semiconductor substrates, such as, forexample, retaining clips, pins, etc. Also, it is to be understood thatsemiconductor substrates received by devices 18 and 20 can be heldwithin separate containers (not shown), with the containers beingreceived by devices 18 and 20. Accordingly, each of devices 18 and 20can retain one or more containers of semiconductor substrates andaccordingly be utilized to treat a batch of contained substrates.Further, it is noted that devices 18 and 20 can receive semiconductorsubstrates by providing a tray that extends between devices 18 and 20and which is configured to retain semiconductor substrates.

Apparatus 10 comprises a circuit 30. Such circuit comprises an electrode32, a power source 34, and a monitor 36. Electrode 32 is inserted withinbath 14 and preferably comprises a material substantially resistant tothe corrosive properties of the bath. Such electrode can comprise, forexample, carbon, platinum or silicon. Power source 34 can compriseeither an alternating current (AC) or direct current (DC) source, andpreferably comprises a DC source providing a power of less than or equalto about 24 volts. The low power is preferably utilized to reduce achance of injury to persons that may inadvertently contact bath 12.Circuit 30 further comprises an electrical connection 38 that extendsfrom electrode 32 through power source 34, past monitor 36 and throughdevices 18 and 20. A last portion of circuit 30 extends from devices 18and 20, through fluid 14 and to electrode 32. Since the conductivematerial of devices 18 and 20 is covered with an insulative protectivematerial, there will, in preferred embodiments, effectively be nocurrent flow within circuit 30 until the protective material of one orboth of devices 18 and 20 is compromised to expose the underlyingconductive material to bath 12. Once the protective material iscompromised, however, electrons will travel from the exposed underlyingconductive material through fluid 14 and to electrode 13, enablingcurrent flow within circuit 30.

Preferably, monitor 36 will be configured to monitor a current flowstate of circuit 30. Specifically, monitor 36 will determine if thecircuit is in a closed state (which enables a current flow), or in anopen state (which does not enable the current flow). If the insulativematerial of devices 18 and 20 is intact (i.e., the underlying conductivematerial is not exposed to fluid 14), circuit 30 will be in an openstate. On the other hand, if a breach occurs in the insulative materialover one or both of devices 18 and 20 to allow underlying conductivematerial to be exposed to fluid 14, circuit 30 will be in a closedstate.

In the shown embodiment, an alarm 40 is coupled with monitor 36. Alarm40 can be configured to generate one or both of a human-detectableaudible signal or a human-detectable visible signal in response tomonitor 36 detecting a closed circuit state. Accordingly, alarm 40 canbe configured to alert a user that the insulative material on one orboth of devices 18 and 20 has been compromised. The user can thenreplace the devices 18 and 20 before the conductive material of devices18 and 20 is exposed to a corrosive fluid 14 for a sufficient period oftime to cause extensive structural damage to the conductive material ofdevices 18 and 20 or significantly contaminate the fluid.

Alarm 40 can be considered to be a circuit-state indicator. Suchindicator is configured to be different when circuit 30 is closed thanwhen circuit 30 is open. Accordingly, the indicator signals a breach inthe insulative material of devices 18 and 20 by changing from anontriggered state to a triggered state in response to circuit 30changing from being in the open state to being in the closed state. Asindicated above, the difference between a non-triggered state and atriggered state can be a difference in one or both of an audible orvisible signal. For instance, the non-triggered state could comprise noaudible signal, and the triggered state could comprise a specificaudible signal. In other aspects, the non-triggered state could comprisea specific audible signal, and the triggered state could comprise adifferent audible signal than that of the non-triggered state. In otherexemplary configurations, alarm 40 could comprise a signal on a displayscreen, or could comprise shut-down circuitry configured to removedevices 18 and 20 from fluid 14 upon detection of a change in circuit 30from open to closed.

Although circuit 30 is described above as changing from open to closedupon a breach in the protective material of devices 18 and 20, it is tobe understood that the change does not have to be from a condition of nocurrent flow to a condition of some current flow. Instead, the changecould be in an amount of current flow. In other words, the open statecan preclude all current flow, or just a predetermined level of currentflow. Further, as the amount of current flow could increase with anincreasing number, or size, of breaches in devices 18 and 20, monitor 36could be configured to quantitate an amount of current flow anddetermine if the current flow exceeds a predetermined value which isgreater than zero. Such predetermined value could be chosen tocorrespond to a value at which significant structural damage toconductive materials of devices 18 and 20 is found to occur.Accordingly, the sensitivity of circuit 30 can be adjusted relative toan amount of damage to the insulative protective material of devices 18and 20 which will trigger the alarm 40 coupled with monitor 36. Ofcourse, apparatus 10 could be constructed without alarm 40, and insteadhave values from monitor 36 displayed so that such values could beregularly checked by users of device 10. It is noted that thepredetermined value referred to above can be zero in applications inwhich it is desired to have apparatus 10 with extremely high sensitivityto breaches in the insulative protective material of devices 18 and 20.

Another embodiment of the invention is described with reference to FIG.2. In referring to FIG. 2, similar numbering will be utilized as wasutilized in describing the embodiment of FIG. 1, with differencesindicated by different numbers. FIG. 2 shows an apparatus 50 comprisinga bath 12, and a pair of semiconductor substrate receiving devices 18and 20. Apparatus 50 comprises a circuit 60 comprising a power source34, a monitor 36, and an electrode 32. A difference between circuit 60of FIG. 2 and circuit 30 of FIG. 1 is that each of devices 18 and 20 isseparately connected to monitor 36 in circuit 60, whereas the devices 18and 20 were connected to monitor 36 through a common connection incircuit 30. The separate (or parallel) connection of devices 18 and 20to monitor 36 can enable monitor 36 to indicate which of devices 18 and20 has had a protective coating compromised. Such can enable a personutilizing apparatus 50 to replace only the one of devices 18 and 20which has had the protective material compromised, rather than replacingboth of such devices.

Monitor 36 of apparatus 50 is connected to an alarm 40. Alarm 40 can beconfigured to generate a different alarm if device 18 has its protectivecoating compromised than if device 20 has its protective coatingcompromised. Accordingly, alarm 40 can be configured to identify whichof devices 18 and 20 has had a protective coating compromised.

In the discussion above, apparatuses 10 (FIG. 1) and 50 (FIG. 2) aredescribed as comprising two semiconductor substrate receiving devices(18 and 20). It is to be understood that the invention encompasses otherembodiments (not shown) where only one semiconductor receiving device isprovided, or wherein more than two semiconductor receiving devices areprovided.

It is noted that in either of the embodiments described above, if thebath has a low concentration of electrolyte, additional power can beprovided to create a current from the conductive material of devices 18and 20 to electrode 32 when the protective insulative material ofdevices 18 and 20 is compromised. Accordingly, methodology of thepresent invention can be utilized with bath solutions which wouldgenerally not be considered conductive, such as, for example, deionizedwater having a conductivity of 18.26 megohm-cm.

Although the invention is described with reference to exemplaryembodiments pertaining to semiconductor wafer processing, it is to beunderstood that the invention is not to be limited to semiconductorwafer processing methods except to the extent that such limitation isrecited in the claims which follow. The invention can be utilized fordetecting a breach in a protective material in any application in whicha conductive material (such as a metal) is coated with an insulativeprotective material (such as a plastic) and immersed in an electrolyticsolution. It can be particularly desirable to detect breaches in theprotective material if the electrolytic solution is corrosive for theconductive material.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A semiconductor substrate receiving apparatusconfigured to establish a current flow state within an electrolyticbath, comprising: a conductive substrate support to be submerged in theelectrolytic bath, the conductive substrate support coated withelectrically insulative material; an electrode within the electrolyticbath; a power source configured to provide current flow between theelectrode and conductive substrate support; and a circuit-stateindicator comprising an audible signal activated during the current flowbetween the electrode and conductive substrate support.
 2. The apparatusof claim 1 further comprising at least two conductive substratesupports.
 3. The apparatus of claim 1 further comprising at least twoconductive substrate supports and circuitry being configured to indicatewhich of the at least two conductive substrate supports has had itselectrically insulative material compromised.
 4. The apparatus of claim1 further comprising a monitor configured to monitor the current flowstate to determine if an electrical closed state or an electrical openstate exists between the electrode and conductive substrate support. 5.The apparatus of claim 4 wherein the electrical closed state indicatesthe electrically insulative material is not compromised and theelectrical open state indicates the electrically insulative material iscompromised.
 6. The apparatus of claim 4 further comprising an alarm inelectrical connection with the monitor and configured to change from anon-triggered state to a triggered state if the current flow statechanges from being in the electrical open state to being in theelectrical closed state.
 7. The apparatus of claim 1 wherein the powersource comprises a direct current power source.
 8. The apparatus ofclaim 1 wherein the power source comprises an alternating current powersource.